Structure including a plurality of cells of cured resinous material, method of forming the structure and apparatus for forming the structure

ABSTRACT

A structure that includes a plurality of cells of a cured resinous material. Each cell is joined to at least one other cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Application No.PCT/US01/11170, filed Apr. 5, 2001 which claims the benefit of priorfiled co-pending U.S. Application No. 60/196,027, filed on Apr. 7, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure that may be formed of aplurality of resinous cells, a method and an apparatus for forming sucha structure. The structure may be formed in place where it is to beutilized.

2. Description of Related Art

In many situations, it may be desirable to form a structure in placewhere it is to be utilized. Sometimes, a structure is preformed and thenassembled in place. One proposed application of such structures is inouter space. For example, it has been proposed to form spacecraft orportions of spacecraft from prefabricated inflatable structures.Prefabricated inflatable structures have also been proposed for formingstructures on other celestial bodies, such as moon bases and undergroundcaverns. Such structures have also been proposed for use in terrestrialapplications.

Space-based structures that are assembled and/or formed in place caninclude a plurality of layers of material with various functions. In thecontext of a spacecraft, the structures can include layers for meteoriteresistance, gas retention for inflatable structures, layers for helpingthe structure to maintain its shape, layers to help retain heat, and/orlayers for other functions.

Space based structures have been proposed that are prefabricated andthen inflated in space. For example, satellites have been proposed anddeployed, which include an inflatable structure. According to oneexample, the satellite referred to as Explorer XIX, which was launchedin December 1963, included a 20 inch inflatable structure. The structurewas inflated with gas and included 40 gore plies of preform over ahemispherical mold. The skin was a four-ply laminate consisting ofalternating layer so aluminum foil and mylar film, each 0.5 or 0.013 mmthick. The inflatable structure maintained its shape after evacuation ofthe inflating gas.

Other satellites formed from inflating structures include the ECHOsatellites, such as the PAGEOS satellite launched in June of 1966. Thissatellite included 84 gore plies sealed with adhesive tape. Thestructure was inflated utilizing a mixture of subliming powders. Duringground-based tests, the inflated structure was found to differ from thedesigned dimensions by less than one-half of one percent. This accuracywas obtained at least in part by utilizing an accurate gore ply pattern,by maintaining seal tolerances and by lowering sealing temperature.

Another proposed use of inflatable structures is as a protectiveexpandable enclosure for astronauts. In particular, an enclosure wasbuilt that included a composite wall having an inner three-barrierpressure bladder for gas retention, a four-ply Dacron cloth structurallayer, a 2-inch thick polyether foam meteoroid barrier, and a film-clothlaminate outer cover with thermal coating. The expandable composite wallcould be structurally bonded to a rigid aluminum honeycomb sandwichfloor.

Another example includes an inflatable antenna. The antenna as it hasbeen proposed includes a large, pressurized antennae. In a structureshaped by internal pressure, using a low modulus plastic film, thepressure level decreases with the third power of the linear dimension.As a result, lost inflatant mass would decrease with increasing antennasize. This would make it possible to build low-mass inflatable systemswith 5- to 10-year lifetimes. One design incorporates a stabilizationtorus, with a pressure sufficiently high to warrant the use of arigidizing structure.

Another proposal includes an inflatable, space-rigidized structure(ISRS). One example of this structure is a 10-m antenna reflector. Theantenna consisted of a thin, fiber-reinforced composite lamina. Thematerials used were a lightweight KEVLAR cloth in an imide-modified,catalytically cured, cycloaliphatic epoxy resin, which may be curedeither thermally or by an external gaseous catalyst. The area mass ofthe resulting composite wall, including a plastic foil gas barrier, wasof the order of 0.1 kg/mz.

According to another example, the SOLARES was a 1000 m diameter flatlight-reflective membrane stretched by an inflatable toroidal hoopstabilized by tension lines to two masts normal to the membrane at thecenter. Also, an inflatable antenna has been created that includes alarge microwave or light collecting or reflecting dish fabricated usingan inflated torus for the rim and either parabolically shaped orspherical shaped plastic membranes attached to the torus. The membraneswere stretched to shape by air pressure. The concave surface wasmetallized to produce the desired microwave reflectivity.

It has been proposed to form a structure by blowing large bubbles inspace using self-rigidizing liquids. This would allow the fabrication oflarge flat structures. Then, self-rigidizing foam could be used toinflate and subsequently rigidize inflatable structures.

As apparent from the above discussion, a number of methods forfabrication of structures in space have been postulated. A number of theproposals have involved inflated structures, clever mechanisms thatunfold and lock into position, or polymeric based component systems thatcan be processed real time. Each has benefits and drawbacks.

Attempts to inflate a structure have been successful in initialdeployment, but require a method of maintaining the pressure orstabilizing the structural elements once the gas has been used toposition them. Long-term gas supply requires dedicated mission payloadcapacity. The gas must be maintained in a leak free containment or thestructure will collapse. Any gas that does leak or diffuse through thestructure over time will be a possible contaminant to sensors and solarcell arrays. This is true even for a structure that only depends on thegas for deployment, not to maintain structural rigidity.

A mechanical approach has been successful in a number of cases, but itis limited to smaller structures due to the inefficiencies inherent injoints, fasteners and sliding surfaces. A number of deployment failureshave occurred that were traced to environmental effects, such as thermalexpansion and contraction or to tribological effects.

It has also been proposed to fabricate polymeric-based compositestructures in space, by pultruding or extruding the materials through aheated processing device. However, the energy requirements for heatingcan be very taxing on a spacecraft's power system. The residual stressesdeveloped in a composite structure as it is heated during curing andcooled to ambient, and possibly very low, temperatures add complicationto the design. Another detrimental factor of such techniques isoutgassing of the resin as it is processed. Again, this presents acontamination issue. One approach to get around this issue has been theexploration of using ultraviolet (UV) curing resin systems. The primarydrawback to this technology has been the inability to develop a processthat allows the resin to be cured with UV while the composite materialis being compacted. A composite structure cured with no compacting loadwill have a substantially reduced performance due to low fiber volumefraction.

Another research path has been the use commercial closed cell foamtechnology to produce a lightweight rigid structure that expands toshape during processing. Unfortunately, all of the commercial foamingtechnology produces a gas that can become a contaminant as it diffusesthrough the polymer. A two component foaming technology is verydifficult to control in terms of cell size and cell size distributionthroughout a structure's cross-section.

With respect to boom structures utilized in space, boom structurescurrently are considered to fall into one of the five categoriesdiscussed below. The simplest boom structure is based on the use oftension members, typically wire. These structures have limitedapplication, as the spacecraft must be spinning. Centrifugal forcedeploys and maintains the boom structure.

To date, probably the most common type of boom is the tubular boom. Itconsist of a thin metallic strip which is spool-wound during storage,but upon controlled release is automatically formed into a tubular shapegiving it its stiffness. The tubular boom is, however, limited by itsbuckling strength at the root.

Another type of boom is the telescoping boom. A telescoping boom istypically shorter but has greater strength than a tubular boom. Atelescoping boom is typically deployed using a lead screw or similartype device.

A fourth type of boom employs a series of continuous longerons, whichare bent and twisted into a helix for stowage in a cylindricalcontainer. Batten frames are arranged perpendicular to the longerons toprovide the required separation, while diagonal cables are used toprovide the required shear stiffness. This technology is limited by theamount of strain that can be placed on the longerons in the storagecontainer. Booms of this type have been built in excess of 100 feetlong.

The final boom type is similar to the one previously described except ituses articulated longerons instead of continuous longerons. In this typeof structure, the longerons are in segments and connected with hingedjoints to the batten frames. This approach also utilizes diagonal cablesto provide the required shear stiffness.

SUMMARY OF THE INVENTION

The present invention provides a structure that includes a plurality ofcells of a cured resinous material. Each cell is joined to at least oneother cell.

Additionally, the present invention provides a method of forming astructure. According to the method, a plurality of individual cells areformed. Each cell includes a mass of uncured resin. Some of the cellsare contacted with others. The resin is cured.

Furthermore, the present invention provides an apparatus for creating astructure that includes a plurality of cells of cured resinous material.The apparatus includes a plurality of resin flow apertures arranged topermit cells formed at one aperture to contact cells formed at directlyadjacent apertures. The apparatus also includes a resin flow controlmember arranged in each resin flow aperture and operable to control aflow of resin from the resin flow apertures.

Still other objects and advantages of the present invention will becomereadily apparent by those skilled in the art from a review of thefollowing detailed description. The detailed description shows anddescribes preferred embodiments of the present invention, simply by wayof illustration of the best mode contemplated of carrying out thepresent invention. As will be realized, the present invention is capableof other and different embodiments and its several details are capableof modifications in various obvious respects, without departing from theinvention. Accordingly, the drawings and description are illustrative innature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and advantages of the present invention will be more clearlyunderstood when considered in conjunction with the accompanyingdrawings, in which:

FIGS. 1 and 2 represent perspective views two different embodiments of astructure formed according to the present invention in the process ofbeing formed;

FIGS. 3 and 4 represent perspective views two different embodiments of astructure formed according to the present invention;

FIG. 5 represents an overhead view of an embodiment of a forming plateaccording to the present invention;

FIG. 6 represents a cross-sectional view of an embodiment of a resinflow aperture, resin flow control member, fluid flow aperture and fluidflow control member according to the present invention;

FIG. 7 represents an overhead view of the embodiment illustrated in FIG.6;

FIGS. 8-10 represent cross-sectional views the embodiment of theapparatus illustrated in FIGS. 6 and 7 at various stages of anembodiment of a process according to the present invention;

FIG. 11 represents a cross-sectional view of an embodiment of acell-retaining member according to the present invention;

FIG. 12 represents a perspective view of another embodiment of astructure according to the present invention; and

FIG. 13 represents a perspective view of an embodiment of a device thatincludes an embodiment of a contour forming surface according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention can satisfy the need or desire to form structuresin place. Additionally, the present invention can fulfill the need tocreate lightweight high strength structures. In particular, the presentinvention can be utilized to form elongated lightweight high strengthstructures. While the present invention may be particularly useful inspace, it may be utilized for terrestrial as well as underseaapplications.

Structures according to the present invention include a plurality ofcells of cured resinous material. The cells may be arranged in aplurality of planes. Each plane may include the same or a differentnumber of cells. The cells may all be aligned with each other in adirection perpendicular to the planes. Alternatively, the cells may bearranged aligned in another direction. For example, the cells in oneplane could be arranged with their centers spaced one-half cell diameteraway from the cells in an adjacent plane. The cells could be aligned indirections other than in a direction perpendicular to the planes. Also,the cells in one plane may be aligned with each other. In some cases,the cells in one plane or among the planes could be arranged in anotherpattern. While the cells may be arranged in a variety of patterns, theytypically are arranged in a pattern.

Notwithstanding the above, any arrangement of cells may be possible. Thedescription herein is illustrative and not exhaustive. Those of ordinaryskill in the art may be able to determine any number of arrangements ofcells without undue experimentation once aware of the disclosurecontained herein.

The structures according to the present invention that are formed of aplurality of cells may have any desired shape. According to someembodiments, the structures are tubular having any desiredcross-sectional shape. The structures could also be solid with anyshape. Some embodiments can include a network of cells, such as a beamof crisscrossing lines of cells. The structures can be hollow or solidmasses of cells.

FIGS. 1-4 and 12 illustrate exemplary embodiments of structuresaccording to the present invention. Along these lines, FIG. 1illustrates a rectangular mass of cells. On the other hand, FIG. 2illustrates a solid tube of cells. The structures shown in both FIGS. 1and 2 are in the process of being formed, as described below in greaterdetail. FIGS. 3 and 4 illustrate two different embodiments of a beammember according to the present invention. Each beam member includes acylinder of cells. The cylinder shown in FIG. 3 has an inner volume andan outer surface that both have a hexagonal cross-section. On the otherhand, the exterior and/or interior surfaces of such structures may havedifferent contours.

Other examples of structures include a solid structure, a hollow tubularstructure, a structure with struts at orthogonal angles across the tube,an open grid work like a truss, a helical structure and a cross helicalstructure. In reality, the structures that may be formed according tothe present invention are almost endless. The arrangement of cells toform a structure would be determined and then the cells assembledaccordingly. FIG. 12 illustrates such an embodiment. Along these lines,FIG. 12 illustrates an embodiment of a structure according to thepresent invention that includes a latticework of cells. This embodimentincludes a different arrangement of cells from layer to layer.

Cells according to the present invention typically have a generallyspherical shape, at least during formation and prior to contacting othercells. However, the cells may have other shapes. In a finishedstructure, cells could have a generally hexagonal, square or triangularshape. The shape of each cell may at least in part depend upon therelative positions of adjacent cells and the presence or absence ofcells in positions adjacent a cell. If a cell abuts another cell it willhave a different shape than if no cell is adjacent the cell. The cellson the top, bottom and sides will have a spherical outward-facingcontour. On the other hand, if a cell is surrounded on all sides byother cells, the cell could be generally cube shaped. Alternatively, thecell could have a shape with hexagonal sides.

On a side of a cell that does not abut an adjacent cell, the surface ofthe cell may have a curvature similar to the surface of a sphere. As aresult, a structure formed according to the present invention typicallywill have a bumpy, rounded surface. If necessary, a portion of thefabrication device could be designed to constrain the external dimensionof the outermost cells before they are cured, causing their walls toform against a non-stick surface, and thus producing a smooth outersurface. On the other hand, where a first cell abuts against anothercell, the first cell may have a more planar contour or a sphericalcontour indented toward the center of the first cell. Where two cellsabut against each other, the cells do not really have a surface sincethey actually contact each other.

It is important to keep in mind that since the cells abut each other andmay contact each other during the formation process, prior to curing, insituations where one cell abuts another, the cells may not be consideredto have a surface. Along these lines, the uncured resin from one cellmay intermingle with the uncured resin from an adjacent cell during theformation process. In such a case, neither cell may actually have a wallat that point. However, where a cell in the process of being formedcontacts an existing cell, then each cell may be considered to have awall, but the walls are in contact. In some cases, adjacent cells mayonly contact each other at a single point.

The size of the cells may vary, depending upon the application. In somecases, dense networks of small cells may be more desirable in astructure than utilizing larger cells. For example, the embodimentsshown in FIGS. 3 and 4 have walls that include a plurality of smallcells. Rather than having walls many cells thick, this embodiment couldhave a wall one cell thick. Typically, the cells making up a structureall have the same or substantially the same size. However, it is alsopossible to have different size cells in one structure. One embodimentincludes a plurality of larger similarly sized cells arranged in apattern, with a plurality of smaller cells arranged in a regular patternto close up spaces among the larger cells. For example, the larger cellscould be arranged in a square pattern with smaller cells arranged in theinterstices between the larger cells.

The cells according to the present invention may have a variety ofinternal structures. For example, a cell may have a uniform, orsubstantially uniform, composition throughout. In other words, the cellmay be a solid mass of resin. Alternatively, a cell may include a shellof resin.

If a cell includes a shell of resin, the shell may be filled withanother material. The shell could be filled with a fluid, includingliquid or gas. Alternatively, the shell could be substantially empty.

In cases where the cell includes a shell, the interior of the shellcould have an interior pressure similar to an ambient pressure outsidethe shell. In space, this could mean that the interior pressure of thecell is quite low. On the other hand, the interior pressure of the cellcould be lesser or greater than the ambient pressure surrounding thecell and the structure including the cell. In the event that the shellis filled with gas, the gas could be the same gas utilized to inflate amass of uncured resin. Alternatively, other gas(es) could be utilized.In underwater applications, the cells could be filled with seawater. Oneskilled in the art could determine a suitable fluid to fill a cell withas well as an appropriate internal pressure suitable to an applicationonce aware of the disclosure contained herein without undueexperimentation.

Resinous materials that may be utilized include commercially availablepolymers. The type of polymer utilized may vary based upon the desiredstructural properties of the finished structure. Typically, polymerswould be desired that have high stiffness, or modulus, such as for manyspace-based applications. In some applications, greater flexibility maybe desired. Also, polymers that have high strength typically aredesirable, such as in many space-based applications. However, in someapplications high strength may be less important or desirable.

Another physical property that may be of importance is the coefficientof thermal expansion. In some cases, it would be desired to have a lowcoefficient of thermal expansion In some cases, the propensity of thepolymer to release gas that may be utilized to inflate the resin may beimportant. Along these lines, it may be desirable that the cured resinnot release gas at a high rate. This can help to maintain an internalpressure within a cell if the cell has a shell that is filled with gas.In such applications where it is desired for the interior of the cell tohave an internal pressure equal to the pressure outside the cell, thenthe outgassing characteristics can be important.

Another property of the resin that can be important is the coefficientof thermal expansion. If it is desired that the structure have a highdegree of thermal stability then it will be desirable for thecoefficient of thermal expansion to be low. However, the coefficient maybe high. Typically, it is desired for the resin to have a uniformcoefficient of thermal expansion. This can help to eliminate deformationof a structure formed with the cells as the cells undergo heating andcooling.

The environmental durability of the cured resin may be taken intoconsideration. Typically, it is desirable for the cured resin to have ahigh resistance to degradation by environmental elements, such as, forexample, radiation, temperature, impact from particles. In differentapplications, different factors may be of greater or lesser importance.For example, in space, radiation and particle resistance may be ofparamount importance. On the other hand, in an underwater application,resistance to the corrosive nature of seawater may be significant.

Other factors that may be of importance to selecting a resin can includemoisture or biological growth resistance, electrical conductivity,electrical insulation, RF transparency, optical properties, chemicalsusceptibility, and/or other properties.

In some cases, the properties of the resin when uncured may also be ofimportance. Among the characteristics that can be considered areviscosity, surface tenacity, cure rate and/or others. In some cases, theease with which the uncured resin may be stored and handled may beimportant.

Another factor that may be important in identifying polymers to utilizecan include the type energy required to cure the polymers. For example,in space-based applications, where ultraviolet radiation is abundant,resins cured with ultraviolet radiation may be the most desirable. Inother cases, thermosetting resins may be desirable.

The structure of a cell may also influence the resin utilized. Forexample, if the cells are to include a shell, then it may beparticularly important to select a resin that will permit the formationof repeatable dimension stable cells.

In the particular example of a truss or strut for use in a spacestructure, UV cured epoxies may work better than other resins. Otherresins that could be utilized in a space-based application includepolyurethanes, acrylics, and silicones, particularly UV cured examplesof each of these. However, it is important to understand that thediscussion herein only provides examples of factors that may beconsidered in selecting a resin for use in a structure according to thepresent invention. Other factors may alternatively or additionally beconsidered in selecting a resin. Those of ordinary skill in the art,once aware of the disclosure contained herein would be able to determinean appropriate resin or mixture of resins with required propertieswithout undue experimentation.

The type of resin utilized may also take into account the processutilized for forming a cell according to the present invention. A methodfor forming a structure according to the present invention includesforming a plurality of individual cells each including a mass of uncuredresin. The cells may be formed in planes, with each cell in a planebeing formed at about the same time. Alternatively, whether formed inplanes or not, the cells may be formed individually at different times.When the cells are formed can depend at least in part upon the apparatusutilized to form the cells.

Some of the cells are contacted with some of the other cells. Whichcells are contacted with which others will depend at least in part uponthe type of structure that is being formed. Along these lines, in astructure that includes a solid mass of cells, such as the structureshown in FIG. 1, most cells will contact many other cells. On the otherhand, if the structure is a strut, many cells will contact fewer othercells.

After forming the masses of resin, the resin is cured. The curing may becarried out by exposing the resin to whatever type of energy cures theresin. In some cases, where the masses are formed in planes, each massin a plane may be cured at the same time. Alternatively, the masses maybe formed and cured at different times.

As the masses are formed, they may be formed in the shape of a sphere.In embodiments that include solid cells of resin, the resin may beformed as a mass.

Alternatively, where the cells include a shell, a mass of resin may beformed. The mass may then be inflated by injecting fluid into the massof resin. Depending upon the embodiment, the fluid may be liquid or gas.An amount of liquid sufficient to inflate the resin mass to a desiredsize in injected into the resin masses. Typically, the gas will notreact with the resin and/or the curing process. Examples of such gassescan include nitrogen, argon, helium and/or any other gas that isnon-reactive with the resins or the curing process. However, if the gasis needed in the curing process, for example to catalyze or as areactant, then other gases may be utilized. For example, hydrogen oroxygen could be utilized in such an embodiment. Such gases may also beutilized if it were desired to create an explosive structure. If thefluid is a liquid, then the fluid could be solidified after injection.In some embodiments, one fluid is utilized to inflate the masses ofresin and another fluid is injected into the cured cell. In suchembodiments, the fluid utilized to inflate the resin mass is evacuatedfrom the resin mass after inflation and curing or the resin.

In embodiments of structures described above that include planes ofcells, the structures may be formed one plane at a time. As each planeis formed, it is joined to the plane formed just prior. Cells in eachplane are contacted with the cells in an adjacent plane as needed toform the desired structure. As described above, the cells in adjacentplanes may be arranged in a line perpendicular to the planes.Alternatively, the cells in adjacent planes may be arranged in a lineinclined with respect to a line perpendicular to the planes.

The planes may be formed with the same number or a different number ofcells. Some cells in a structure may have the same number of cells insome planes and different numbers in other planes. The masses of resinare created and cured until the desired structure is formed.

The present invention also includes an apparatus for forming a structureaccording to the present invention. Other apparatuses may also beutilized to form a structure according to the present invention.

An apparatus according to the present invention includes a plurality ofresin flow apertures. The resin flow apertures are arranged to permitcells formed at one aperture to contact cells formed at adjacentapertures. A resin flow control member is arranged at each resin flowaperture to control the flow of resin from the resin flow aperture.

The resin flow control member could include any suitable valve that cancontrol the flow of resin. The opening and closing of the resin flowcontrol member is controlled to permit an amount of resin to flow outthat is sufficient to form what ever size cell is desired.

If it is desired that the cells according to the present inventioninclude a shell rather than a solid mass of resin, then an apparatusaccording to the present invention may also include a fluid injectionport to inject fluid into the uncured resin. By injecting fluid into theresin, the mass of resin may be inflated. Flow of fluid through thefluid injection port and into the uncured resin may be controlled by afluid flow control member. The fluid flow control member may be any flowcontrol member suitable to control the flow of a fluid. As describedabove, the fluid may be gas or liquid. If the fluid is a gas, then anyvalve or other member capable of controlling the flow of gas could beutilized. Similarly, if the fluid is a liquid, then any valve or othermember could be utilized to control the flow of liquid. When a sphere isformed the surface tension tends to either keep expanding the sphere ifthe material allows or to fail the sphere as it reaches the tensilestrength of the membrane formed.

The fluid flow control member can control flow of fluid into and out ofthe cell, as described above. Along these lines, if it is desired toequalize the pressure of the interior of the cell with the ambientpressure outside of the cell, then the fluid flow control member couldcontrol the flow of fluid out of the cell. Additionally, if anotherfluid is introduced into the cell after curing, then the fluid flowcontrol member can control the flow of fluid back into the cell.

To form embodiments of the present invention that include a plurality ofcells arranged in planes, the resin flow apertures may be arranged in aforming plate. Such a plate can include a plurality of fluid flowapertures arranged in any pattern. Some embodiments may include resinflow apertures arranged in concentric circles. Other embodiments caninclude resin flow apertures arranged in a rectangular grid. Any desiredarrangement of resin flow apertures may be utilized. If the pattern ofholes that generate individual cells is switched on and off in variousgeometric patterns, different morphology structures can be formed.

FIG. 5 illustrates an embodiment of a forming plate according to thepresent invention. Along these lines, FIG. 5 illustrates a forming plate1 that includes a plurality of resin flow apertures 3. The resin flowapertures are arranged in a hexagonal grid.

To form a structure, flow of resin may be turned on and off in the resinflow apertures in the plate. For example, if a beam including a skeletonof members were being formed, some times, resin might flow out of onlythree or four of the apertures that would be arranged at the corners ofthe beam and a few apertures arranged in the center of the beam to forminterior skeletal members. To form a cylindrical shape such as thatshown in FIGS. 3 and 4, a ring of apertures would be permitting resin toflow to form the wall of the structure, with all other apertures beingclosed off entirely during the entire process of forming the structure.Of course, resin would only periodically flow from the apertures as eachplane is formed.

Some embodiments of an apparatus according to the present inventioninclude resin flow apertures with positions that are alterable. Suchapertures may not be formed in a plate. However, the position of theplate may be altered to alter the position of the resin flow apertures,as well. This can permit a desired cell pattern to be produced as well.Even if the position of the resin flow apertures is alterable, the flowof resin may be controlled to flow from only selected apertures.

The resin flow apertures may all have the same diameter. This can permitthe apparatus to form cells of resin having the same diameter.Alternatively, the apertures may have different diameters. In somecases, the diameter of the resin flow apertures may be varied to permitthe apparatus to form different size cells.

According to an embodiment that includes a forming plate that includes aplurality of resin flow apertures, a resin flow control member may bearranged at each aperture. The resin flow control members may becontrolled to generate the desired resin flow pattern.

FIG. 6 illustrates an embodiment of a resin flow control member that maybe included in a forming plate. Along these lines, FIG. 6 illustrates aportion of a forming plate 5. A resin flow aperture 7 extends throughthe forming plate 5.

This embodiment of a resin flow control member includes a shutter plate.The shutter plate includes two elements 9 and 11. Resin 13 is arrangedin an area beneath the shutter plates. The shutter plates may be movedlaterally in the view shown in FIG. 6 to permit resin to flow out of theresin reservoir located beneath the shutter plates. The broken line 15indicates resin flowing from the resin flow aperture. The resinreservoir may be pressurized to cause the resin to flow out of the resinreservoir. After a sufficient amount of resin has flowed out of theresin flow aperture, the shutter plates maybe moved laterally to closeoff the flow of resin.

The embodiment shown in FIG. 6 may be utilized to form cells thatinclude a shell of cured resin. Along these lines, the embodimentincludes a fluid injection port 17. A fluid flow control member 19 isarranged in a fluid supply line 21. Fluid may be injected into the resinas the resin flows out of the resin flow aperture. Alternatively, thefluid may not be injected into the resin until all of the resin hasflowed out of the resin flow aperture and the flow of resin has been cutoff.

The amount of gas needed to inflate the resin cell depends upon theamount of resin and the desired size of the inflated cell. Inembodiments that produce uniform size cells, the amount of gas could becontrolled to always be the same, as could the amount of resin flowingfrom the aperture. This could permit a structure to be more easily,quickly, and cheaply formed.

Although the fluid injection port is arranged adjacent the resin flowaperture, it may be arranged in any location that permits the fluid tobe injected into the resin as it flows out of the resin flow aperture.Typically, the fluid injection port is located to inject fluid into theresin on a side of the resin cell that faces the next plane of cells.

As described above, the fluid that may be injected to inflate the resinmay be withdrawn. Withdrawing the fluid may be carried out for a varietyof reasons. Withdrawing the inflating fluid may be carried out toequalize the pressure within a cell to the ambient pressure outside thecell. The fluid may also be withdrawn to conserve the inflating fluidthat might be lost to the environment. Such would typically be the casein space-based applications. Also in space-based applications,withdrawing an inflating gas can serve to prevent diffusion of the gasout of the cell structure and subsequent condensation back onto coldsurfaces on a spacecraft, its solar cells or instruments. Also, in aspace-based application, reuse of the inflation gas will minimize themass and volume of materials needed to construct a structure accordingto the present invention in space. This can result in lower costs andfree up payload capacity for other functions, instead of gas that willbe thrown away.

FIG. 7 illustrates an overhead view of the embodiment shown in FIG. 6.

Other arrangements are possible for the resin flow control and fluidflow control. Along these lines, the present invention could include aniris valve to control the flow of resin. The resin and inflating fluidcould flow through nested or concentric tubes or nozzles. Any othersuitable dispensing mechanism could also be employed.

The thickness of the wall produced by injecting a fluid into a resin maydepend at least in part upon the viscosity of the resin. Utilizing aresin having a known viscosity that maintains a film when inflated intoa “bubble”, the wall thickness of the bubble will be determined by abalance of forces. The gas pressure outward, the viscosity of the resinresisting flow, the effect of gravity or any other inertial effectpulling on the resin mass, and the time over which it can flow.Typically, it would be desired to quickly inflate and cure the resinbefore the bubble walls can thin out or develop a thickness gradientfrom top to bottom. In space this would not be as big of a problem,although studies of bubbles in weightlessness have still shown amovement of material in a bubbles wall based on surface tensiondifferences from point to point.

FIGS. 8-10 illustrate the embodiment shown in FIGS. 6 and 7 at variousstages of the formation of a cell that includes a shell of cured resin.Along these lines, FIG. 8 shows the shutter valve as it has movedlaterally to initiate the flow of resin. In FIG. 9, the shutter valvehas closed and the fluid has been injected into the resin to inflate theresin. In FIG. 10, the resin has been inflated a desired amount andenergy to cure the resin impacts on the resin, as indicated by arrows 23and 25.

In space, the sun could act as the source of energy to cure the resin,if the resin is cured by the available wavelength(s) of ultravioletradiation. Alternatively, a source of curing energy could be included inthe apparatus. While the resin may be self-curing, if it requires energyto be cured, the energy source could produce whatever type of energy isrequired. As described above, the resin could be cured by heat, visiblelight, electron beam, microwave or other form of energy.

In embodiments that include a source of curing energy, the apparatuscould include a source of curing energy. The source of curing energycould be located where ever it would be effective. For example, a UVlight distribution system could be arranged above the opening either onthe surface of the plate or built into the plate between the resin flowapertures. The UV light distribution system could include, for example,fiber optic or light pipes arranged in patterns to distribute the curinglight to all of the surfaces of a just formed cell. FIGS. 8-10illustrate an embodiment of an apparatus according to the presentinvention that includes a source of curing energy 31 arranged on thesurface of the forming plate. The energy source shown in FIGS. 8-10includes a distribution light pipe for supplying UV curing energy. Suchan energy source can permit distribution of energy to each cell,independent of the size of the structure and/or the cells. This canaddress problems associated with supplying curing energy equally to allcells as the cross-sectional size of a structure grows. A variation ofthis embodiment features the curing energy source that is integral tothe plate surface.

After curing the resin, the forming plate may be moved away from thecured resin cells a distance of about one cell thickness. This canpermit the next plane of cells to be formed and to contact the precedinglayer of cells. To facilitate formation of the structure, an apparatusaccording to the present invention can include one or more cellretaining elements to retain the cells after curing and as the formingplate moves one cell layer away. FIG. 11 illustrates an embodiment of acell-retaining element 27. Any variety of means could be utilized toretain the cells. For example, a vacuum could retain a cell to acell-retaining element.

FIG. 11 also illustrates a hole in the resin cell 29 that may remainfrom the withdrawal of the fluid flow port from the resin cell aftercuring. The succeeding layer of cells can seal that hole. The processcould be controlled to cause additional resin to flow into the hole toseal it to help ensure that little or nothing flows into or out of thecell as the fluid injection line is withdrawn from the cell. This wouldtypically be carried out at least with the cells of a final plane of astructure and cells that do not have an adjoining cell in directlysucceeding plane of cells.

When forming a structure according to the present invention, it may bedesired to impart a particular contour to surfaces of cells that do notcontact adjacent cells. For example, it may be desired that the exteriorof a structure built of cells have a smooth contour. An embodiment of adevice according to the present invention could include one or moreelements for imparting a desired contour to the cells as they are formedbefore the resin is cured. For example, a device could include one ormore elements that would define an outermost extent of a structure to beformed. For example, as the device could include an element having acell-engaging surface at each location where a cell could be formed. Asthe cells of resin are formed, they would come into contact with thesurface. As the resin contacts the ring, the surface of the resin cellwould take on the contour of the cell. The surface(s) could be movableso that where ever it is desired that a cell have the desired contour,the surface could be moved. One embodiment could include a ring thatwould define the outermost extent of a structure to be formed. Otherembodiments could include one or more plates, pads, and/or otherelements.

The surface(s) could be coated with a material to help prevent the resinfrom sticking. For example, the surface(s) could be coated with afluoropolymer. One example of a fluoropolymer is polytetrafluoroethyleneor TEFLON. Any suitable material could be utilized to help prevent theresin from sticking to the surface(s).

If it were desired that the structure have a curved surface, then adevice according to the present invention could include a ring that hasa curved surface that faces the resin cells. On the other hand, if itwere desired that the exterior of a structure include a plurality offlat surfaces, such as the structure shown in FIG. 3, then the ringcould include a similar number of flat surfaces. The ring or othersurfaces could have any desired contour.

During the formation of cells, a contour forming surface(s) could bepositioned in a desired orientation(s) relative to the cell(s) adjacentwhere cells are to be formed, such as in the vicinity of the formingplate described herein. The resin could then be expelled from the resinflow apertures in the forming plate. As resin is fed through theaperture, it will contact the contour forming surface and as more resinis fed or the resin is inflated, the surface of the resin that contactsthe contour forming surface will take on the contour of the surface. Byutilizing one or more contour forming surfaces, a smooth or less bumpysurface can be imparted to the cells. The contour forming surface(s)could then be moved to a position contact subsequent layers of cells, ifdesired.

FIG. 13 illustrates an embodiment of an apparatus that includescontour-forming elements. The contour-forming elements include twosemi-circular rings 31 and 35. As can be seen in FIG. 13, as a resincell increases in size, the outer most portion of its surface willcontact the contour-forming elements and, as a result, the outer surfaceof the cell will take on the contour of the contour-forming elements.

FIGS. 1 and 2 illustrate two embodiments of a structure during anembodiment of a process for forming the structure and utilizing anembodiment of an apparatus. Along these lines, FIGS. 1 and 2 illustratetwo radiation sources 2 and 4 that each produce radiation 6 and 8 to acton the structures 10 and 16 as they are formed. FIGS. 1 and 2 alsoillustrate a forming plate 12. Indexing or manipulating device 14 canmove the cured structure away from the fabrication surface of theorifice or forming plate or retain the structure as the orifice platemoves away from the structure.

It is not necessary that an indexing or manipulating device extendentirely along a structure. The indexing or manipulating device couldinclude an annular collar that is located near the plate and surroundsthe structure being fabricated. As discussed above, other embodiments ofan indexing or manipulating device are also possible.

A few significant advantages of the present invention include that theycan produce a very light weight structure with adequate buckling andbending properties to accommodate structural loads. Due to use of asmall reusable pressurization system and minimal mass of the polymersused the payload weight can be dramatically reduced over that ofdeployable bags or other systems. The present invention can also producea structure with a compressive wall stiffness exceeding that of typicalcollapsible inflated structures. Also, an inflated structure's wallmaterial can become creased or permanently deformed where it was foldedfor storage before deployment, thereby reducing its column buckling loadcapability. The present invention can be applied to space structuresincluding platforms, arrays and antennas.

The present invention can be utilized for ultra-lightweight boomstructures for space in proposed ultra-lightweight structures and spaceobservatories. Along these lines, the present invention can be utilizedto form boom structures in space that are very lightweight and stillhave high buckling strength area. The present invention can be adaptedto specific requirements for deployable boom structures that take up aminimum of space and can be easily deployed, while having high bucklingstrength. This is at least in part facilitated by a processing techniquethat will permit deployment/extrusion of a structure and curing in-situ.Significantly, the present invention can be applied to other spacestructures, such as the construction of space stations or thefabrication of space colonies on other worlds.

The foregoing description of the invention illustrates and describes thepresent invention. Additionally, the disclosure shows and describes onlythe preferred embodiments of the invention, but as aforementioned, it isto be understood that the invention is capable of use in various othercombinations, modifications, and environments and is capable of changesor modifications within the scope of the inventive concept as expressedherein, commensurate with the above teachings, and/or the skill orknowledge of the relevant art. The embodiments described hereinabove arefurther intended to explain best modes known of practicing the inventionand to enable others skilled in the art to utilize the invention insuch, or other, embodiments and with the various modifications requiredby the particular applications or uses of the invention. Accordingly,the description is not intended to limit the invention to the formdisclosed herein. Also, it is intended that the appended claims beconstrued to include alternative embodiments.

1-14. (canceled)
 15. A method of forming a structure, the method comprising: forming a plurality of individual cells each comprising a mass of uncured resin; contacting some of the cells with others; and curing the resin.
 16. The method according to claim 15; further comprising: injecting fluid into the masses of uncured resin to inflate the cells of resin.
 17. The method according to claim 16, wherein the fluid is a liquid.
 18. The method according to claim 16, wherein the fluid is a gas.
 19. The method according to claim 17, further comprising: solidifying the liquid after injecting it into the cells.
 20. The method according to claim 15, wherein the structure is formed by sequentially forming the cells in a plurality of planes and joining cells in each plane to cells in an adjacent previously formed plane of cells.
 21. The method according to claim 20, wherein the number of cells formed in each plane differs.
 22. The method according to claim 20, wherein cells in a plurality of adjacent planes are arranged in different positions orthogonal to the planes.
 23. The method according to claim 20, wherein cells in a plurality of adjacent planes are aligned in a direction perpendicular to the planes.
 24. The method according to claim 16, further comprising: evacuating the fluid from the interior of the cells after curing the resin.
 25. The method according to claim 24, further comprising: injecting another fluid into the cells after evacuating the fluid utilized in inflating the cells.
 26. The method according to claim 25, wherein the fluid is a gas.
 27. The method according to claim 25, wherein the fluid is a liquid.
 28. The method according to claim 27, further comprising: solidifying the liquid after injecting into the inflated cell.
 29. The method according to claim 24, wherein the fluid is evacuated until an interior of the cells has a gas pressure substantially similar to an ambient pressure external to the cells.
 30. The method according to claim 25, wherein the other fluid is injected into the cells until an interior of the cells has a gas pressure substantially similar to an ambient pressure external to the cells.
 31. The method according to claim 15, wherein forming the cells of uncured resin comprises: feeding the uncured resin through a plurality of resin flow apertures in a plate.
 32. The method according to claim 15, wherein all of the cells are formed of a similar size.
 33. The method according to claim 15, wherein curing the resin comprises exposing the resin to at least one of ultraviolet radiation, heat, visible light, an electron beam, and microwave radiation. 